The natural history of multiple sclerosis: a geographically based study 8:Familial multiple sclerosis

We have examined the demographics and long-term outcome of 1044 patients wi th sporadic and familial multiple sclerosis in a population-based cohort fr om London, Ontario. The mean follow-up was 25 years in duration, and by thi s time most patients had reached the unambiguous endpoint scores of the Kur tzke disability status scale (DSS), DSS 6, 8 or 10, An affected family memb er was identified in 19.8% of the total population, and this subgroup was f urther divided arbitrarily into the following three groups by the type and number of relatives affected: (i) first degree only; (ii) first degree plus others; (iii) second or third degree. The outcome in these groups was comp ared with that for those patients who, at a mean 25 year follow-up, had no relatives known to be affected, Familial cases closely resembled those rema ining sporadic in both demographics and outcome, although onset in the most heavily loaded families was earlier and male/female ratio was greater. The times to DSS 6, 8 and 10 did not differ significantly when sporadic, famil ial and familial subgroups were compared. These results provide no clinical support for viewing familial multiple sclerosis as distinct from the spora dic form. The observed recurrence rate for siblings in a strictly defined e pidemiological sample was 3.5%, much as projected. These results validate t he recurrence risks which have previously been derived from age-corrected d ata for these first-degree relatives.